In the Nether, you recover the adventurer's journal entries long ago. They were immediately taken captive upon entrance into this realm, and thrown into the prisons. The king of that realm then brought them for questioning, inquiring of their world. Soon, one of them was take for a "private interrogation," but was no longer the same. He had been corrupted by the Nether King via some form of magic and was now the Nether King's soldier.

The three remaining adventurers escaped, finding an armory and a forge to arm themselves. They needed a way to escape, so they headed into the Nether King's mountain fortress and to the library in order to learn more. Their previous friend, now corrupted soldier, led an assault on them, but failed. However, one more of their group was taken in the attack, leaving two of the group alive and normal, and two corrupted by the Nether King.

The remaining two adventurers discovered that there were crystals all around that housed some dimensional properties... But they were being corrupted, shown by a new red glow. The corruption in the crystals is the magic that the Nether King used to corrupt some of the adventurers. But more than this, they learned the Nether King planned to open a portal and corrupt the Overworld, leading to his own inter-dimensional domination.

The remaining two adventurers climbed the mountain to one large crystal on the top, and upon arriving were again attacked by their two former friends. One of them was taken. There was now only one adventurer uncorrupted, and he left one final journal entry at the top of that mountain: a plea for help, and a warning to learn from his group's mistakes. And here, you find this journal entry. The journey to find and defeat the Nether King is yours now, please succeed.